1. Field of the Invention
The present invention pertains to tools for use in subterranean wells. Specifically, the present invention pertains to tools suitable for making new hole in a well, cleaning out well conduits, and possibly reshaping or reaming well conduits or holes. More specifically, the present invention pertains to such well tools suitable for use with continuous coiled pipe operations but which may advantageously be used with any suitable fluid supply line, including conventional jointed pipe. As used herein, the term "fluid" is intended to include both liquids and gases.
2. Background of the Prior Art
Drilling a well requires expensive equipment and operation. Usually, the drill string comprises joints of pipe which are connected together as drilling progresses. In the past, it has been necessary, when changing a drill bit or in other operations, to pull the drill string, disconnecting and stacking the joined pipe. Such operations have generally required an expensive derrick and a considerable amount of time.
In the past, even working over a non-productive or malfunctioning well has required equipment capable of pulling strings of pipe and disconnecting the joints thereof. To eliminate derricks and associated equipment, some workover or remedial operations have been handled by running various tools into the well on a cable. However, cable workover methods have several limitations, including the inability to utilize fluid flow in the remedial operations.
In recent years, continuous pipe or tubing units have been developed to eliminate some of the problems of conventional workover operations. In the continuous tubing units, a continuous string of small-diameter pipe or tubing is coiled on a reel device and the continuous pipe is fed through an injector device which straightens the tubing and feeds it from the reel down into the well. Such an operation eliminates the need for a derrick and for the time-consuming operation of connecting and disconnecting joints of pipe. Examples of coiled tubing units may be seen in U.S. Pat. Nos. 3,116,781 and 3,313,346.
Coiled tubing units have been used for several types of workover operations. For example, wells having sand bridges which are filled with sand from top to bottom may be cleaned by injecting the continuous pipe into the well while circulating fluids therethrough. An example of such apparatus and method may be seen in U.S. Pat. No. 3,791,447. Coiled tubing units are also often used to "kick wells off," in place of gas-lifting or swabbing, by injecting nitrogen or natural gas into the well or by replacing workover fluid with diesel or lease crude. An example of such apparatus and method may be seen in U.S. Pat. No. 3,722,594. Production zones may be acidized, inhibited, sand consolidated, gravel packed, squeezed off or partially plugged back to shut off bottom water using coiled tubing units. Foreign matter, such as paraffin, may be removed from the tubing by circulation of hot oil or other solvents through continuous coiled tubing units. It will be appreciated that such units are highly flexible in workover operations.
However, there may be situations where circulation of a fluid through a coiled tubing unit will not remedy the problems of a potentially productive well. For example, the well tubing may become plugged with inoperative equipment or foreign matter which cannot be dissolved or washed out by circulation of fluids. In other cases, the production tubing itself may be corroded, deformed, or otherwise defective. In addition, although coiled tubing units are extremely flexible in workover operations, they have not been very suitable for drilling or making new hole in a well. This is probably due to the torsional stresses involved and the impractability of rotating a string formed from coiled tubing with the conventional drill bits and other rotary tools which are presently available.